Among the class of epoxides, ethylene oxide, also known as EO, EtO, ETO, anprolene, dihydrooxirene, 1,2-epoxyethane, oxacyclopropane, oxane, oxidoethane, oxiran, is an industrial chemical used in sterilizing medical items, fumigating spices, and manufacturing other chemicals. Pure ethylene oxide is a colorless gas at room temperature and a mobile, colorless liquid below 54° Fahrenheit. Sold as a mixture with either carbon dioxide or fluorocarbon 12, ethylene oxide has been used as an antimicrobial pesticide since the 1940s. Ethylene oxide kills microorganisms by denaturing their proteins and subsequently modifying their molecular structure. This activity allows ethylene oxide to be effective as a sterilant.
Ethylene oxide is known to be highly toxic. The acute (short-term) effects of ethylene oxide in humans consist mainly of central nervous system (CNS) depression and irritation of the eyes and mucous membranes, and nausea, vomiting, neurological disorders including seizures, convulsions and coma, bronchitis, pulmonary edema, and emphysema at high concentrations. Chronic (long-term) exposure to ethylene oxide in humans can cause irritation of the eyes, skin, and mucous membranes, and problems in the functioning of the brain and nerves. Some human cancer data show an increase in the incidence of leukemia, stomach cancer, cancer of the pancreas, and Hodgkin's disease in workers exposed to ethylene oxide.
The US Department of Labor Occupational Safety and Health Administration (“OSHA”) has set stringent guidelines aimed at protecting workers performing operations in an environment potentially contaminated with ethylene oxide. The Permissible Exposure Limit (“PEL”) for ethylene oxide has been established at 1.8 mg/m3 (approximately 1 ppm). As a result, effective, low cost means of removing ethylene oxide from ambient streams of air is needed.
One method of removing ethylene oxide from ambient streams of air is to use impregnated, activated carbon as a filtration media. The impregnated, activated carbon is known to exhibit a strong affinity for a wide variety of organic chemicals in an ambient air stream. However, under conditions of high relative humidity (i.e., greater than about 50% relative humidity), the absorption capacity of impregnated, activated carbon is largely restricted. Under such conditions, the excessive amount of water vapor severely hampers the ability of the activate carbon to effectively absorb organic chemicals including ethylene oxide.
Depending on the environment and environmental conditions, the water content associated with ambient air can vary over a wide range, from less than about 5% to greater than about 95% relative humidity (RH). Although a number of media, such as, for example, activated carbon and resins, are capable of removing ethylene oxide from dry air, these materials fail to effectively filter ethylene oxide under conditions of high relative humidity.
For this reason, there is a need to provide an enhanced process for removing epoxides including ethylene oxide, propylene oxide, and related compounds from process streams (e.g., ambient air streams) over a wide range of temperature and relative humidity, and especially in the presence of high relative humidity. There is a further need for an enhanced process for removing epoxides including ethylene oxide, propylene oxide, and related compounds from process streams (e.g., ambient air streams) that is relatively cost efficient, safe and easy to make, use or implement, and does not require extensive handling, maintenance and care.